In 1857, at the request of the Tokugawa Shogunate, a group of Dutch engineers began work on the Nagasaki Yotetsusho, a modern, Western-style foundry and shipyard near the Dutch settlement of Dejima, at Nagasaki.[4] This was renamed Nagasaki Seitetsusho in 1860, and construction was completed in 1861. Following the Meiji Restoration of 1868, the shipyard was placed under control of the new Government of Meiji Japan. The first dry dock was completed in 1879.

In 1884, Yataro Iwasaki, the founder of Mitsubishi, leased the Nagasaki Seitetsusho from the Japanese government, renaming it the Nagasaki Shipyard & Machinery Works and entering the shipbuilding business on a large scale. Iwasaki purchased the shipyards outright in 1887. In 1891, Mitsubishi Heavy Industries - Yokohama Machinery Works was started as Yokohama Dock Company, Ltd. Its main business was ship repairs, to which it added ship servicing by 1897.[5] The works was renamed Mitsubishi Shipyard of Mitsubishi Goshi Kaisha in 1893 and additional dry docks were completed in 1896 and 1905.[4]

The Mitsubishi Heavy Industries - Shimonoseki Shipyard & Machinery Works was established in 1914. It produced industrial machinery and merchant ships.[6]

The Nagasaki company was renamed Mitsubishi Shipbuilding & Engineering Company, Ltd. in 1917 and again renamed as Mitsubishi Heavy Industries in 1934. It became the largest private firm in Japan, active in the manufacture of ships, heavy machinery, airplanes and railway cars. Mitsubishi Heavy Industries merged with the Yokohama Dock Company in 1935.[5] From its inception, the Mitsubishi Nagasaki shipyards were heavily involved in contracts for the Imperial Japanese Navy. The largest battleshipMusashi was completed at Nagasaki in 1942.

The Kobe Shipyard of Mitsubishi Goshi Kaisha was established in 1905. The Kobe Shipyard merged with Mitsubishi Heavy Industries in 1934. The Kobe Shipyard constructed the ocean liner Argentina Maru (later repurposed as the aircraft carrierKaiyo), and the submarines the I-19 and I-25.[7]

Following the dissolution of the zaibatsu after the surrender of Japan at the end of World War II, Mitsubishi divided into three companies. Mitsubishi Nagasaki became West Japan Heavy Industries, Ltd. The Nagasaki Shipyard was renamed Mitsubishi Shipbuilding & Engineering Co., Ltd. in 1952.[4] The Mitsubishi Kobe Shipyard became Central Japan Heavy Industries, Ltd. in 1950.[7]

In 1964, the three independent companies from the 1950 break-up were merged again into one company under the name of Mitsubishi Heavy Industries, Ltd. The Nagasaki works was renamed the Nagasaki Shipyard & Engine Works. The Kobe works was renamed the Mitsubishi Heavy Industries - Kobe Shipyard & Machinery Works.[8]

In 1970, MHI's automobile parts department became an independent company as Mitsubishi Motors.

MHI participated in a ¥540 billion emergency rescue of Mitsubishi Motors in January 2005, in partnership with Mitsubishi Corporation and Mitsubishi Tokyo Financial Group.[9][10] As part of the rescue, MHI acquired ¥50 billion of Mitsubishi Motors stock, increasing its ownership stake to 15 percent and making the automaker an affiliate again.[9]

MHI entered talks with Hitachi in August 2011 about a potential merger of the two companies, in what would have been the largest merger between two Japanese companies in history.[13][14] The talks subsequently broke down and were suspended.[15]

In November 2012, Mitsubishi Heavy Industries and Hitachi agreed to merge their thermal power generation businesses into a joint venture to be owned 65% by Mitsubishi Heavy Industries and 35% by Hitachi.[16][17] The joint venture began operations in February 2014.[16][17]

In June 2014 Siemens and Mitsubishi Heavy Industries announced their formation of joint ventures to bid for Alstom's troubled energy and transportation businesses (in locomotives, steam turbines, and aircraft engines). A rival bid by General Electric (GE) has been criticized by French government sources, who consider Alstom's operations as a "vital national interest" at a moment when the French unemployment level stands above 10% and some voters are turning towards the far-right.[18]

In the 1950s the company began to re-enter the aerospace industry in earnest. Along with other major Japanese companies it was involved in design and production of the NAMC YS-11, the first Japanese airliner to enter production after World War II.[19] In 1956 work started on the design of the Mitsubishi MU-2, which became the company's first postwar aircraft design.[20]

In the civil aircraft sector, MHI develops and manufactures major airframe components, including fuselage panels for the Boeing 777 and composite-material wing boxes for the 787. In the space systems sector, MHI is the producer of the H-IIA and H-IIB launch vehicles, Japan's main rockets, and provides launch services to JAXA related to the launch vehicles. The company is also involved in the International Space Station program.

The nuclear business of MHI operates facilities in the cities of Kobe and Takasago in Hyogo Prefecture and in Yokohama, Kanagawa Prefecture. It also operates a nuclear fuel manufacturing plant in Tōkai, Ibaraki which processes 440 Metric tons of Uranium per year.

MHI has also developed the Mitsubishi APWR design. MHI has also signed a memorandum of understanding with Areva for the establishment of a joint venture, Atmea, for their next reactor design ATMEA1.[24]

MHI has also been selected as the core company to develop a new generation of Fast Breeder Reactors (FBR) by the Japanese government.[25] After that announcement was made, MHI established a new company, Mitsubishi FBR Systems, Inc. (MFBR) specifically for the development and realization of FBR technology, starting what is likely to be the most aggressive corporate venture into FBR and Generation IV reactor technology.[26]

MHI is currently developing a $15.8 billion nuclear power plant in Sinop, Turkey in partnership with Itochu and Engie, which would be its first overseas nuclear project.[27]

MHI attempted to acquire the energy business of Alstom in 2014 in order to develop its service network in Southeast Asia. MHI remains interested in acquisitions in the crude oil and gas sectors as of 2015.[28] Following financial difficulties at Areva, MHI announced in 2015 it will make a proposal to take a minority ownership stake in Areva.[29]

MHI has installed more 3,282 MW worldwide until December 2009, mainly turbines with 1 and 2.4 MW.[31] The company is developing 7-MW-turbines for offshore wind power. Tests are planned for 2013 in Europe.[32]